Polymeric material



tion of new fiber-forming polymers.

Patented Aug. 12, 1941 POLYMERIC MATERIAL Wallace Hume Carothers,deceased, late of Wilmington, Del., by the Wilmington Trust Company,Wilmington, Del., executor, assignor to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware No Drawing.Application September 19, 1938, Serial No. 230,724

14 Claims.

This invention relates to synthetic polymeric materials, and moreparticularly to synthetic linear interpolyamldes.

This application is a contlnuation-in-part of U. S. P. 2,130,948, filedApril 9, 1937, which is a continuation-in-part of application SerialNumber 74,811 now U. S. P. 2,190,770, filed April 16, 1936. Thisapplication also is a continuation-inpart of application Serial Number91,617, filed July 20, 1936 and since abandoned, and of applicationSerial Number 125,889, filed February 15, 1937, now U. S. P. 2,188,332.

This application is concerned with certain of the interpolyamidesdescribed in the above mentioned applications. For a betterunderstanding of the present invention, reference may be had first tothe simple polyamides derived from the reaction of a single diaminewithya single dibasic acid or from the polymerization of a single aminoacid, this latter type of polyamide being described in Patent 2,071,253.These polyamides are characterized by high melting point, pronouncedcrystallinity, and

and the phenols. They yield filaments capable of being cold drawn, thatis drawn below their melting point, into fibers showing upon X-rayexamination orientation along the fiber axis. The same properties whichare advantageous for the manufacture of fibers, however, make itdifficult to prepare clear sheets from these polyamides or to use thepolyamides in coating compositions and other compositions which requirethe use of a solvent. Acids and phenols cannot be used advantageously assolvents in coating compositions and the like.

01 the interpolyamides described in the above .mentioned applicationthose prepared from three components, e. g. two diamlnes and on dibasicacid, or one diamine and two dibasic acids, although they have lowermelting points than the simple polyamides, do not have the widesolubility and compatibility characteristics of the four-componentlnterpolyamides which are also described in that application and whichform the subject matter of the present claims. Except for their lowermelting points the three-component interpolymers more closely resemblethe simply polyamides than they do the four-component interpolymers.Interpolyrners prepared from more than four components resemble thefourcomponent interpolymers.

This invention has as an object the prepara- A further object is toprepare from diamines and dibasic insolubility in, most solvents exceptmineral acids, formic acid,

acids interpolyamides having wider solubility characteristics, lowermelting points, and less pronounced crystallinity than the simplepolyamides. A still further object is the preparation of useful articlesfrom these polymers. Other objects will appear hereinafter.

These objects are accomplished by heating to reaction temperature atleast four polyamideforming reactants, at least one of which is adiprimary diamine and at least one other of which is a dicarboxylic acidor an amide-forming derivative of a dibasic carboxylic acid, the amineand acid reactants being used in substantially equimolecularproportions, until a polymeric product is obtained which is capable ofbeing formed into continuous filaments.

By the term polyamide-forming reactants is meant diamines having atleast one hydrogen atom on each amino group, dicarboxylic acids,amide-forming derivatives of dibasic carboxylic acids, polymerizablemonoaminomonocarboxylic acids, and amide-forming derivatives ofmonoaminomonocarboxylic acids, including caprolactam. A salt of adiamine and a dibasic acid will be considered as representing twopolyamideforming reactants.

By substantially equimolecular proportions of acid and amine reactantsis meant that not more than 5 molar per cent excess of either reactantis employed. In other words, the reaction mixture must not containsubstantially more than 5% excess of either amino or acid groups ortheir equivalents.

Through the practice of this invention the above drawbacks of the simplepolyamides can beovercome without sacrificing such desirable propertiesas good thermal stability, strength, and pliability by preparing thepolyamides from a mixture of at least four polyamide-forming reactants,preferably two diamines and two dibasic acids. These products, whichwill be referred to herein as interpolymers or more specifically asinterpolyamides, have much lower melting points than the correspondingsimple polyamides and are less crystalline. This lower crystallinity isevidenced by the following facts: (1) X-ray diagrams of theinterpolymers show a fainter crystalline pattern than in the case of thesimple polyamides, (2) the interpolymers are more resinous in characterthan the simple polymers, (3) melt over a wider range, (4) and giveclearer films, i. e. films in which the crystallinity is much lessapparent. Another difference between the interpolyamides and the simplepolyamides is that cold drawn filaments of the former tend to retractwhen heated at temperatures considerably below their melting points.This property gives the interpolyamides interesting felting qualities.The interpolymers are further characterized by greater solubility inorganic solvents. In addition to being soluble in formic acid and thephenols, the solvents for the simple polyamides, the interpolymers aresoluble in alcohols, particularly when hot, and in alcohol-chlorinatedhydrocarbon mixtures. They are also soluble in unsaturated alcohols, e.g. methallyl alcohol and methyl ethyl ethynyl carbinol. In addition tobeing more soluble than the simple polyamides, the interpolyamidespossess a wider range of compatibility with most modifying agents, e. g.plasticizers and resins. These characteristics, together with inherenttoughness, make these interpolyamides especially valuable in thepreparation of sheet materials and coating compositions.

In the preferred practice of this invention two diamines and twodicarboxylic acids are amideiorming derivatives of dibasic carboxylicacids (ester, half-ester, acid halide, anhydride, or amide), the amineand acid reactants being present in substantially equimolecular amounts,are heated at amide-forming temperatures, generally in the range ofl20-300 C., until the product has a sufficiently high molecular weightto exhibit fiber-forming properties. As in the case of the simplepolyamides, the fiber-forming stage can be tested for by touching themolten polymer with a rod and drawing the rod away; if this stage hasbeen reached a continuous filament of considerable strength andpliability is formed. This stage is generally reached when the polyamidehas an intrinsic viscosity of at least 0.4, where intrinsic viscosity isdefined as in which is the viscosity of a dilute solution of the polymerin m-cresol divided by the viscosity of m-cresol in the same units andat the same temperature (e. g., 25 0.),- and C is the concentration ingrams of polymer per 100 cc. of solution. In general, measurement of theintrinsic viscosity will be the most convenient method for following thecourse of the reaction to determine when the desired degree ofpolymerization has been attained. The interpolymers of this invention donot acquire the properties desired for most 'uses until they havereached the fiberforming stage. In other words, great strength,toughness, pliability, etc., are properties which go hand in hand withthe fiber-tormingproperty.

In general, the interpolymers are prepared most economically fromdiamines and dicarboxylic acids. The reactants are conveniently mixed inthe form of their salts since the salts are crystalline and can bereadily purified. Instead of making a mixed salt using all fourreactants, it is generally preferable to prepare two simple salts eachprepared from one diamine and one dicarboxylic acid and to use themixture of the salts in the polymerization reaction. This method ofpreparation is illustrated in the subsequent examples.

The conversion of a mixture of the diaminedibasic acid salts to theinterpolyamide is carried out in the same manner as the preparation ofsimple polyamides from a single diamine-dibasic acid salt as describedin the application previously referred to. The reaction is carried outby heating the salts at amide-forming temperatures, generally between180 and 300 C., in the presence or absence of a diluent and underconditions which will permit the water formed in the reaction to escape,at least during the last stages of the reaction, until examination of atest portion of the product indicates that it has the desiredfiber-forming properties. As examples of solvents which may be used inthe reaction may be mentioned phenol, the cresols, the xylenols,diphenylolpropane, and o-hydroxy-diphenyl. White medicinal oil is anexample of a non-solvent which may be used. The reaction can also becarried out in the presence of water during the first stage as indicatedin subsequent Examples I-III.

The polyamides of this invention can be prepared in a similar manner byreacting a mixture of diamines and amide-forming derivatives of dibasiccarboxylic acids. In some instances, e. g. in the case of aryl esters ofthe dibasic acid, the polymerization reaction starts at a lowertemperature than in the case of the free acid or salt, sometimes as lowas 50 C.

The polymerization reaction whereby the interpolymers of this inventionare made can be carried out at atmospheric, superatmospheric, orsubatmospheric pressure. Except when the aryl esters of the dibasicacids are used, in which case the by-product is a phenol, the laststages of the reaction, at least, should be carried out under conditionswhich permit the escape of the byproduct of the reaction. This isgenerally done by operating at atmospheric or reduced pressure duringthe last stages of the reaction. Preferably the reaction is carried outin the absence of oxygen, e. g. in an atmosphere of nitrogen, or in avacuum. An antioxidant may be added if desired.

Products of this invention are synthetic linear polyamides. The amidegroups in these polyamides form an integral part of the main chain ofatoms in the polymer. On hydrolysis with hydrochloric acid thepolyamides revert to the reactants from which they were prepared. Inother words, an interpolyamide derived from two diamines and two dibasicacids will yield on hydrolysis with hydrochloric acid a mixturecomprising two diamine hydrochlorides and two dibasic acids.

The following examples, in which parts are by weight, are illustrativeof the preparation and application of the products of this invention.

EXAMPLE I A mixture of 393 parts of hexamethylene diammonium adipate (M.P. 183-184 C.), 560 parts of decamethylene diammonium sebacate (M. P.1'78-180 C.), and 200 parts of water was placed in a stainless steelautoclave. Air was removed from the system by evacuation, followed byfilling the free space with oxygen-free nitrogen and evacuating again.The autoclave was then heated to 265 C. during 1.5 hours. When apressure of 250 lbs. per sq. in. was reached in the autoclave, watervapor was bled off at such a rate that the pressure was maintained at250 lbs. per sq. in. After 2.75 hours heating at this pressure, thepressure was reduced to atmospheric during the course of 0.5 hour andfinally the autoclave was evacuated slowly (0.5 hour) to mm. Aftercooling, the interpolyamlde was removed from the autoclave as anopalescent pseudoresinous solid. It had an intrinsic viscosity of 1.1and a pentrometer softening point from melt and cold drawn 450% had atenacity crease as the composition or the interpolymer approaches thatpossessed by the minimum melting product. Table I gives the meltingpoint, as determined for small particles (fibers) on a heated metalblock in air, for fiber-forming polymers prepared from variousproportions of these two salts.

TABLE I Melting points of various hemmethylene adipamide-decamethylenesebacamide interpolamers Hexamethyle adipamide Decamethylone sebacamide'pomt cc seepeeo IO eseesse Parts by weight of corresponding saltemployed.

EXAMPLE II A mixture of '75 parts of hexamethylene diammonium adipate,75 parts 01' heptamethylene diammonium pimelate (M. P. 163-164" C.), and50 parts of water was placed in an autoclave. Air was removed from thesystem as described in Example I and then the autoclave was heated to255 C. during 1.5 hours. Water vapor was bled off at such a rate as tomaintain a pressure of 160 lbs. per sq. in. for about 0.75 hour. Thepressure was then reduced to atmospheric during 0.5 hour and finally theautoclave was evacuated slowly (0.6 hour) to about 100 mm. Thepolymerlzation was completed by maintaining the autoclave at thispressure for 0.5 hour. The molten interpolyamide was then removed fromthe autoclave by extrusion under pressure through a slot orifice. Themolten polymer coming from the autoclave flowed through an 0.25 inch airwas carried under constant tension by a pair 0! take-oi! rolls placediabout 7 inches below the surface of the water. The ribbon thus obtainedwas very transparent, tough, and quite pliable. The melting point of theinterpolymer in fiber form was l55-157 C. The interpolymer had anintrinsic viscosity of 1.06. Like the interpoly- I amide of Example I,it could be formed into filaments and sheets whose utility was improvedby cold drawing or cold rolling. The interpolymer was soluble inphenols, formic acid, glacial acetic acid, and mineral acids. It wasalso soluble in alcohols and related compounds, and in mixtures ofalcohols and chlorinated hydrocarbons.

ExAllPLa III Following the general methods described in the precedingexamples, a mixture of 192 parts of hexamethylene diammonium adipate,192 parts oi 2,5-dimethylhexamethylene diammoniumalphaalpha'-dimethy1adipate (M. P. 158-160 C.) and parts of water washeated at 250 C. in an autoclave with removal of water during the laststages of the reaction. The resultant interpolymer was formed into aclear, uniform ribbon by the method described in Example II. Theinterpolymer had an intrinsic viscosity of 0.88 and a melting point infiber form of l28-l30 C. Its solubility characteristics were similar tothat of the products of the preceding examples, but this interpolymerwas somewhat more soluble in alcohols and related compounds, e. g.ethers of ethylene glycol. This increased solubility as well as the lowmelting point can be attributed to the branched chain nature of the twoingredients.

EXAMPLE IV A mixture of 5 parts of hexamethylene diammonium adipate and5 parts of decamethylene diammonium p,p-isopropylldenebis-phenoxyacetate, the salt derived from decamethylene diamine and (M.P, 222-224 C.) was heated in a closed vessel for 2 hours at 240-260 C.The low polymer thus obtained was heated for 2 hours more at 240-260 C.under a pressure of 2 mm. The product thus obtained was a very tough,pseudoresinous, transparent polymer. It had an intrinsic viscosity of1.1 and could be spun into filaments which were capable of being colddrawn into strong fibers. The interpolymer melted at 155-l57 C. Moldedfilms of this material were quite clear and pliable. The interpolymerhad the same solubility characteristics as the preceding interpolymers,being soluble in alcohols, alcohol-chlorinated hydrocarbon mixtures,ethers of ethylene glycol, and related compounds besides the customarysimple polyamide solvents, such as phenols, formic acid, and mineralacids.

EXAMPLE V A mixture of 6 parts of hexamethylene diammonium adipate and 4parts of decamethylene diarnmonium isophthalate (M. P. 220-222 C.) washeated in an evacuated tube for 2 hours at 210-230 C. The tube was thenopened and heated for 2 hours more at 230-250 C. under a pressure of 2mm. The interpolymer thus obtained was a clear, pseudoresinous solidwhich melted at -148 C. (in fiber form). The interpolymer was soluble inalcohols and related compounds as well as in the usual polyamidesolvents. It had an intrinsic viscosity 01' 0.73 and could be spun intofilaments capable of being cold drawn into oriented fibers. Films,sheets, etc. of the material were quite tough, transparent, and pliable.Cold rolling on an even speed mill increased the toughness of theseproducts.

EXAMPLE VI A mixture of 5 parts of hexamethylene diammonium adipate, 4parts of hexamethylene diammonium sebacate (M. P, 165-l67 C.), and 1part of hexamethylene diarnmonim. p,p-isopropylidene bis-phenoxyacetate(M. P. 238-240. C.) was heated in a closed vessel for 2 hours at 250-260C. The vessel was then evacuated to 2 mm. and the heating continued for2 hours more at 250-260 C. The hard, bone-like interpolyamide thusobtained had an intrinsic viscosity of 1.05. It melted at l80-185 C. andwas soluble in alcohols and the usual polyamide solvents. Filaments spunfrom the interpolymer were susceptible to cold drawing. Sheets preparedfrom the product were clear, pliable, and tough, particularly whenprepared under quenching conditions and subsequently cold rolled.

It will be apparent that an almost unlimited number of interpolymers canbe prepared in accordance with the process of this invention, since thenumber of combinations possible is very large. In Table II are given themelting points of a number of typical fiber-forming, four-componentinterpolymers, prepared by copolymerization of the salts indicated.

Although interpolymers prepared from more than four components arecharacterized by the same general properties as the four-componentinterpolymers, the four-component interpolymers constitute the preferredembodiment of the invention, since too great a number of reactantscomplicates the problem of securing equivalency of diamines and dibasicacids. Furthermore, for economic reasons it is desirable to limit thenumber of reactants as much as possible. However, when mixed acids areused, e. g. the mixture of azelaic and suberic acids obtained from theoxidation of oleic acid or the mixture of undecandioic and dodecandioicobtained from the oxidation of hydrogenated castor oil, it is frequentlymore convenient to prepare interpolymers containing more than fourcomponents. For example, the salt obtained from reaction of a mixture ofazelaic and suberic acids with a mixture of octamethylene andnonamethylene diamines on heating with hexamethylene diammonium adipategives an interpolymer in which six components are represented.

Of the four-component interpolymers those derived from two diamines andtwo dibasic acids are preferred. As indicated in the examples, theseproducts are readily obtained by copoly merizing two diamine-dibasicacid salts. The preferred reactants for the preparation of interpolymersare diamines of formula NHzCHzR- CHzN'Hz and dicarboxylic acids offormula HOOCCHzR'CHzCOOI-I in which R and R are TABLE II Four-componentmterpolyamzdes Derived lrom Weight ratio of Melting salt I range, Salt I(D=di8.ml110iliill11) Salt [1 (D=diammonium) to salt Ii C.

Hexainethylene D. adipate." Decamethylene D. brassyiate 5o;50 0 -210 D0Pcntamethylene D. glutarate" 60:40 148-150 Do Pentarnethylene D.sebacate. :50 155-157 D Pcutaniethylene D. azeiate 50:50 143-150 D0Heptamethylene D. pimelate 5u;50 155-157 Do Octamethylene D. suberatc..50:50 100-165 D Nonamethylene l). azeiate. 50:50 l-l0-l45 D do 25:75115-118 Do Decamethylene D. dodecaned 50:50 l50-l55 Do 3-tetii'buttyi-hexamethyleno D.fi-ter-butyl- 50:50 115-lla a ma c Do fecamethylene D. isophthalate 70:30 160-165 D0 m-Phenylene D. sebacatenm00:40 122 127 m-Phenylene D. sebacate Decnmcthylcne D. isophthalate30:20 rsonas Instead of preparing the interpolymers of this inventionfrom monomeric reactants as illustrated in the foregoing examples, theycan also be prepared from simple polyamides. This can be done by heatingtwo or more different simple polyamides with water or alcohol underpressure, preferably at a temperature between 180 and 300 C. Under theseconditions partial hydrolysis of the polyamides occurs with theformation of low polyamides and some monomeric reactants, the extent ofthe hydrolysis depending upon the temperature and the quantity of wateror other hydrolytic agent used. The Water or other hydrolytic agent isthen permitted to escape, preferably at a temperature sufficiently highto keep the reaction mass fluid, and the heating is continued atamide-forming temperatures. This causes the hydrolysis products (chieflylow polyamides) to reunite and in so doing they form an interpolymer.This method, which is also useful in blending two samples of the samesimple polyamide, serves as a means for recovering waste or scrappolymer.

divalent hydrocabron radicals and in which R has a chain length of atleast two carbon atoms. Preferably R and R are methylene orpolymethylene groups. However aromatic reactants, e. g.m-phenylenediamine and isophthalic acid, are useful ingredients if ahigh-melting interpolymer is desired. In preparing interpolymers fromaromatic diamines it is frequently desirable to react the diamine withan excess of dibasic acid or acids, preferably two moles of acid foreach mole of amine, and then to react this intermediate with therequired amount of aliphatic diamine or diamines to bring aboutequivalency of amino and acid groups. This procedure is recommended inthe case of aromatic diamines because they react more slowly thanaliphatic diamines.

It should be understood that the interpolymers are not limited to thoseprepared solely from diamines and dicarboxylic acids. If desired.modifying agents such as plasticizers, pigments, resins, delusterants,etc. may be added before, during or after the polymerization. It is alsowithin the scope of the invention to add to the polyamide-formingreactants other polymeri'orming reactants, e. g. hydroxyacids andglycols. Polymerizable monoamino-monocarboxylic acids, e. g.6-aminocaproic acid, and amide-forming derivatives thereof, e. g.caprolactam, may also be used in preparing the interpolymer-s.

For certain purposes it is desifible that the interpolymers beviscosity-stable, i. e. do not alter appreciably in viscosity (molecularweight) when heated at their melting points. Viscositystabie.interpolymers can be prepared by using a small excess (up to molar percent) of the diamine or dibasic acid reactants or by incorporating inthe reaction mixture a small amount, generally 0.1 to 5% of a monoamineor a monocarboxylic acid or derivative thereof. Acetic acid and stearicacid are typical viscosity stabilizers of this class.

The products of this invention can be employed in the preparation offibers for use in the textile art; e.g. in the preparation of knitted,woven, and pile fabrics. Interpolyamides particularly useful for thepreparation of filaments for use in textiles are those having meltingpoints above 200 C. and preferably above 225' C. which may be obtainedby the use of relatively small quantitles of two of the components ofthe interpolymer. For example, interpolyamides based primarily uponpolyhexamethylene' adipamide are most suitable for use as textile fiberswhen the interpolyamide contains 80 or more per cent of thepolyhexamethylene adipamide. These polymers are somewhat easier to spinthan the simple polyamides since they decompose only very slowly attemperatures required to keep them molten, are less sensitive to oxygenat the temperature required for their manipulation, and yet aresufficiently high melting to withstand temperatures of ironingcustomarily employed on fabrics. Like the simple polyamides, theinterpolyamides can be spun from melt or from solution by the wet or dryprocess. Because of the solubility of certain of these materials inalcohols, unsaturated alcohols, alcohol-halogenated hydrocarbonmixtures, and other low-boiling solvents, the interpolymers are moresuitable for spinning from solution than the simple polyamides.

Interpolyamide fibers, like fibers made from simple polyamides, can beused in the prepara-' t on of yarns, metallized yarns, lastex-typeyarns, threads, ropes. braided cords, crepe fabrics, organdies. and imregnated, laminated, or composite fabrics. The laminated fabrics, e. g.for cuffs and collars can be made by securing between two layers ofhigh-melting or infusible fabric a fabric or sheet composed of orimpregnated with interpolyamide and then laminating the product byapplying sufficient heat and pressure to cause the interpolymer tosoften. The polyamide fabrics. sheets, etc., can also be embossed. Sincepol amides are fusible, pieces of polyamide fabric can be combined bymeans of heat, 1. e. by "seam welding. If desired. agents canbeincorporated in the fabric which undergo some change, e. g., a colorchange. at a temperature slightly below the meltin Point of the polymerto act as a.

warning agent in ironing.

BY reason of the fact that cold-drawn filaments of certain of the lowermelting interpolv.. amides tend to retract when heated, they are usefulin making felted articles. Thus, when colddrawn interpolyamide filamentsor staple fibers.

:like, and the mixture is heated, the retraction of the interpolymerfilaments or fibers has a felting action on the mixture.

Fibers of interpolyamides are also useful in the preparation of manyspecialty cloths where severe wear or abrasion is encountered or wherehigh tensile strength both wet and dry is required; for example, in thepreparation of sail cloth, airplane wing fabric, typewriter ribbons,tracing cloth, belting, camera bellows, filter cloths, mothproof bags,laundry and other bags, steam and fire hose, gasket fabrics and gearfabrics for molded gears, surgical dressings, tapes, and stencil screensfor decorating glass. Other uses for fibers in suitable form includepackings for stuiiing boxes, fish nets, hair nets, artificial hair,security paper, and windings for baseballs. The fibers may be long orshort, solid or hollow, and may be combined with other types of fibers.In the form of crimped fibers, the interpolyamides are useful in makingcashmere, worsted suitings, blankets, down and feather substitutes, andthe like.

Owing to the great toughness, pliability, and good clarity of the sheetmaterials prepared from interpolyamides, they are especially useful inthis form, particularly after they have been cold rolled. Typical usesfor this form are wrapping foil, metalized foils, and casings forsausage and other foods. As in the case of simple polyamides, the sheetsare also useful in making leather substitutes, tile substitutes,gaskets, washers, drinking straws, i. e. spiral tubes, goggles,windshields, glass and isinglass substitutes, diaphragms for loudspeakers, etc., raincapes, lamp shades, umbrellas, hats, translucentpicture projection screens, transfer picture base, fiber boardsubstitutes, membranes for musical drums, dialyzing membranes,substitutes for goldbeaters skin, collapsible tubes for soaps, etc.,bottle caps, shoe insoles, fan blades, airplane wings, heat insulation,belting, transparent straps, e. g. for womens underclothes, playingcards, table cloths, e. g. for card tables, printing blankets, acid andalkali shields, and window shades. The interpolyamides are also usefulin the preparation of blown articles such as toys; hollow toilet ware,etc. Ribbons or strips of the interpolyamides are useful as whalebonesubstitutes, and as reeds for weaving chairs and baskets.

The good solubility characteristics of the interpolymers, together withtheir other desirable properties, make them useful as ingredients incoating and impregnating compositions. For example, the interpolymerscan be used to coat paper, cloth, leather, linoleum, regeneratedcellulose sheeting, bookbinding and other materials from melt or fromsolution. Coated cloth is particularly useful for upholstery and bookcloth. The interpolyamides can be used as clear lacquers, e. g. as acoating over other finishes or directly as coatings for wood, metals,cement, etc. In the form of pigmented enamels or paints, they are usefulas a general industrial finish, e. g. in coating machinery, ships,automobiles, houses, cans, printing plates, leather, etc. Interpolymerscan also be used to coat food containers, and other materials whichrequire a water-insensitive, oilor alkali-resistant coating. A furtheruse of polyamide coating compositions is for coating fruit and nurserystock. Rubber is another material to which polyamide coatings can beapplied coats, hospital sheeting, golf balls, coatings, etc. In theporous or blown form the interpolyamides can be used as cork or spongesubstitutes. Further uses for the products of this invention are sizesfor textiles and paper, shoe stiffeners, stiffeners for hats, flameretardants, impregnating agents for wood, modifying agents for paperpulp, modifying agents for lubricants, ingredient in insecticides,substitutes for glass in double windows, glazed chintz, and reliefs forprinting.

It is understood that in all of the above uses the interpolymers may beadmixed with other materials, e. g. plasticizers, pigments, resins,cellulose derivatives, and simple polyamides.

As many apparently widely diiferent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

What is claimed is:

1. A process which comprises heating at reaction temperature apolyamide-forming composition comprising at least four polyamide-formingreactants, at least one of which is a diprimary diamine and at least oneother of which is a substance of the class consisting of dicarboxylicacids and amide-forming derivatives of dibasic carboxylic acids, thecomplementary amide-forming reactants in said polyamide-formingcomposition being present in substantially equimolecular proportions,and continuing said heating until a polymeric product is obtained whichis capable of being formed into continuous filaments.

2. A process which comprises heating to reaction temperature at leasttwo diprimary diamines and at least two different complementaryamideforming reactants selected from the class consisting ofdicarboxylic acids and amide-forming derivatives of dibasic carboxylicacids, the amine and acid reactants being present in substantiallyequimolecular proportions, and continuing said heating until a polymericproduct is obtained which is capable of being formed into continuousfilaments.

3. A process which comprises heating two diprimary diamine-dibasiccarboxylic acid salts derived from different diprimary diamines anddibasic carboxylic acids until a polymeric product is obtained which iscapable of being formed into continuous filaments.

4. A polyamide capable of being formed into useful textile fibers, saidpolyamide being obtained by condensation polymerization from at leasttwo diprimary diamines and at least two different complementaryamide-forming reactants selected from the class consisting ofdicarboxylic acids and amide-forming derivatives of dibasic carboxylicacids.

5. A synthetic linear polyamide having an intrinsic viscosity of atleast 0.4, said polyamide yielding upon hydrolysis with hydrochloricacid a mixture comprising at least four polyamideforming reactants, atleast one of which is a diprimary diamine hydrochloride and at least oneother of which is a dibasic carboxylic acid.

6. A synthetic polyamide capable of being formed into fibers showing bycharacteristic xray patterns orientation along the fiber axis, saidpolyamide upon hydrolysis with hydrochloric acid yielding a mixturecomprising at least two diprimary diamine hydrochlorides and atleasfltwo dibasic carboxy lic acids.

7. A syntheflc polyamide having an intrinsic viscosity of at least 0.4,said polyamide being obtained by condensation polymerization from amixture comprising at least two diamines of formula NHzCHzRCHaNH: and atleast two dicarboxylic acids of formula HOOCCHzR'CHzCOOH in which R andR are divalent hydrocarbon radicals and in which R. has a chain lengthof at least two carbon atoms.

8. A synthetic linear polyamide having an intrinsic viscosity of atleast 0.4, said polyamide being obtained by condensation polymerizationof hexamethylenediamine, decamethylenediamine, adipic acid, and sebacicacid.

9. The synthetic polyamide set forth in claim 5 wherein said diprimarydiamine is an aromatic diamine. 7

10. A polyamide capable of being formed into useful textile fibers whichcomprises the reaction product of at least four polyamide formingreactants, whose complementary amide-forming constituents are present insubstantially equimolecuiar proportions, at least one of which reactantsis a diprimary diamine and at least one other of which reactants is asubstance of the class consisting of dicarboxylic acids andamide-forming derivatives of dibasic carboxylic acids.

11. Filaments, ribbons, sheets, and the like comprising a syntheticinterpolyamide, said interpolyamide being obtained by mutualpolymerization of at least four polyamide-formingreactants whosecomplementary amide-forming constituents are present in substantiallyequimolecular proportions, at least one of which reactants is adiprimary diamine and at least one other of which reactants is selectedfrom the class consisting of dicarboxylic acids and amideformingderivatives of dibasic carboxylic acids.

12. A synthetic linear polyamide having an intrinsic viscosity of atleast 0.4, said polyamide being obtained by condensation polymerizationof hexamethylenediamine, heptamethylenediamine, adipic acid, and pimelicacid.

13. The polyamide set forth in claim 10 wherein at least per cent of thesaid polyamide forming reactants consists of hexamethylene diamine andadipic acid in substantially equirnolecular proportions.

14. The filaments, ribbons, sheets, and the like, set forth in claim 11wherein at least 80 per cent of the said polyamide forming reactantsfrom which the said interpolyamide is obtained consists of hexamethylenediamine and adipic acid in substantially equimolecular proportions.

WILMINGTON TRUST COMPANY,

Executor of the Estate of Wallace Hume Carothers, Deceased,

By ELWYN EVANS,

Vice President.

